Multidrug resistance to antimicrobials as a predominant factor influencing patient survival

https://doi.org/10.1016/j.ijantimicag.2005.12.013Get rights and content

Abstract

The impact of multidrug resistance to antimicrobials was assessed in a cohort of 243 patients with microbiologically documented infections by a variety of susceptible and multidrug-resistant (MDR) species. Multidrug resistance was defined as resistance to more than two antimicrobial agents of different chemical structure. Cox regression analysis was performed to define differences and the significance of any predisposing factors. Overall survival of patients infected by susceptible isolates was prolonged compared with patients infected by MDR isolates (P = 0.013). Mortality rates of infections caused by susceptible and MDR isolates were 4.87% and 16.15%, respectively (P = 0.013); the higher mortality rate for MDR isolates was more pronounced for infections by Klebsiella pneumoniae and Pseudomonas aeruginosa. Mean (± standard error (S.E.)) survival of patients infected by susceptible and MDR isolates in patients without signs of severe sepsis was 28 days and 27.29 ± 0.35 days, respectively (P = not significant). Mean (± S.E.) survival of patients with severe sepsis caused by susceptible and MDR isolates was 7.70 ± 4.62 days and 10.45 ± 2.18 days, respectively (P = 0.048). Diabetes mellitus type 2, the presence of severe sepsis and any underlying malignancy were the most important risk factors affecting survival. It is concluded that infections by MDR isolates were accompanied by higher mortality rates and decreased survival compared with infections by susceptible isolates. Diabetes mellitus type 2 and underlying malignancies were significant co-morbid conditions, whereas survival after infection by susceptible isolates was particularly decreased in the event of severe sepsis.

Introduction

The increased prevalence of multidrug-resistant (MDR) isolates in the nosocomial setting has raised the need for new strategies in the management of nosocomial infections [1]. One dominant question that the clinician often faces nowadays is whether infections by MDR pathogens significantly affect mortality. Few studies have been performed and they are characterised by controversy. Infections by resistant isolates of Staphylococcus aureus [2] and Enterococcus faecalis [3] are accompanied by lower survival rates compared with infections by susceptible isolates of the same species, and a recent meta-analysis of 31 studies concluded that bacteraemia by methicillin-resistant S. aureus (MRSA) led to decreased survival compared with methicillin-susceptible S. aureus (MSSA) [4]. However, a recent study failed to disclose any difference in mortality rates of critically ill patients with nosocomial bacteraemias caused by either antibiotic-resistant or -susceptible Gram-negative pathogens [5].

The controversial results of the above studies raise the need to identify the impact of multidrug resistance on the overall survival of hospitalised patients with severe infections. The present study was designed to clarify this issue.

Section snippets

Study design

In a prospective study for the period January 1997 to January 2000, all patients hospitalised with either a community-acquired or a hospital infection at the 1st Department of Propedeutic Medicine of Laikon General Hospital of Athens were followed-up. Two hundred and forty-three patients with a definite microbiological diagnosis of infection matched for age and sex were considered for further statistical analysis. The study was approved by the Ethics Committee of the Laikon General Hospital of

Results

The demographic data for patients enrolled in the study are shown in Table 1. A total of 82 patients presented with infections by susceptible isolates and 161 with infections by MDR isolates. Mortality rates of infections caused by susceptible and MDR isolates in general were 4.87% and 16.15% (P = 0.013). Mortality rates in relation to the species of pathogen are given in Table 2.

Comparative survival curves of patients infected by susceptible or MDR pathogens are shown in Fig. 1. Mean (± standard

Discussion

The emerging problem of multidrug resistance in everyday nosocomial practice renders the question of whether resistant isolates are more or less virulent compared with susceptible isolates of the same species [14], [15]. The present study attempted to resolve that question in a cohort of 243 patients (Table 1). All enrolled subjects presented with a microbiologically defined infection by a variety of species of susceptible or MDR isolates. Statistical analysis attempted to exclude probable

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